Automatic telephone-exchange system



Dec. 19, 1922. 1,438,960. I. w. LAIIIG EI AL.

AUTOMATIC TELEPHONE EXCHANGE SYSTEM.

ORIGINAL FILED AUG.29. 1904. 5 SHEEISSHEET I.

L/nco KM aff/'7: Char/9J L. Good/am DeC. 19,- 1922. 1,438,960.

J. W. LATTIG ET AL.

AUTOMATIC TELEPHONE EXCHANGE SYSTEM.

ORIGINAL HLED AUG 29 1904. 5 sHEErsn-ASHEET 2.

Mllllll Cha/*45d* L. Good/w77.I ky Am/ Dec. 19, 1922.

1. W. LATTIG ET AL.-

AUTOMATIC TELEPHONE XCHANGE SYSTEM.

ORIGINAL FILED AUG.29, 1904.

llllllwlhhillw @hay/9S l.. (9004/0/77.

5 SHEETS-SHEE1 3y Dec. 19,1922. i 1,438,960. J. W. LATTIG ET AL.

AUTOMATIC TELEPHONE EXCHANGE SYSTEM.

ORIGINAL FILED AUG.29I T904. 5 SHEETS-SHEET 4.

Cop/wofr Trab/f Cormac/70h vlljsiterated Der. 1922;

"stares 'er raast JACOB W. LATTIG, OF BETHLEHEM, PENNSYLVANIA, AND CHARLES L. GOOD- RUM, OF NEW YORK, N. Y., ASSIGNORS TO WESTERN ELECTRIC COMPANY, INCORPO- RATED, OF NEW YORK, N.V Y., A CORPORATION OF YORK.

AUTOMATIC .TELEPHONE-EXCHANGE SYSTET. l

Original application filed August 29, 1904, Serial No. 222,657. Divided andap'plication led October 12, l1917, Serial No4 196,125. Divided and this application led December 24,' 1921. Serial No. 524,724.

To all whom t may concerti.:

Be it known that we, JACOB W. LA'r'rrc and CHARLES L. GooDRUM, citizens of the United States, residing at Bethlehem, in 5 the county of Lehigh and vState of Pennsylvania, and at New York, in the county of New York and State of New York, respectively, have invented certain new and useful Improvements in Automatic Telephone-EX- change Systems, o'f which the following is a full, clear, concise, and exact description.

This invention relates to telephone eX- change systems, and is a division of application Serial No.r 196,125 filed October 12,

1917, which is a division of application Serial No. 222,657 ,filed August 29, 1904.

In multi-office .telephone systems it is the practice to supply talking current to the subscribers lines from the ofiicesgin which the subscribers lines terminateand to inter* connect the oiiices by` trunks consisting of only two conductors. These trunk conductors'are also used tov control the settin of the automatic switches at the distant o ce.

It is the object of this invention to employ .these same ltrunk conductors to operate an electro-responsive device at the originating oiiice at a certain stage in the process v of building up a connection to operate metering or supervisory equipment, thus avoiding the necessity of providing additional conductors for this purpose.

In accordance with this invention an electro-responsive device is connected to each` outgoing trunk which device is responsive to a change brought about inthe trunk circuit at a certain stage in the process of build ing up the connection, as for example when the called party answers, and which device in operating causes the operation of call charging equipment associated with the call' relays.

tral oiiice meter individual to the calling.A

line, which meter thus records the call.

`Preferably each inter-oiiice trunk is provided with two polarized relays. The reresponse of the called party applies current to the trunk which flows in-the proper direction to operate the other of said polarized This relay in operatingsupplies talking current to the calling, line which'is not of the proper direction to operate the said meter magnet.

Our invention is illustrated in the accompanying drawin s, wherein the same letters gram of a trunk circuit leading vfrom a'irs-t selector toa second selector; Fig. 2 is a diagram of the circuits of a second selector;'v

Fig. 3 is a diagram of the circuits and connections ofV a connector; and Fig. 4 is a diagram cfa subscribers line, its substation apparatus, and its first selector, the connection to the multiple bank of the connector of Fig. 3 being shown in heavy lines at the left. p

We have not illustrated the switch mechanism in detail as regards its mechanical parts, more particularly because our invention is not limited to av specific switch, but may be practiced with an one of a'number of automatic switches. s the circuits are shown, however, for the sakevof illustration we will refer to the following patents, in which the so-called Strowger type of switch is shown, this being with some modifications hereafter referred to, adapted for use with these circuits. a Oct. 5, 1897, Strowger, Lundquist and Erlck- 'first selector for thatA line; Fig. llis a dia- The patents are: 591,201`

son; 638,249, Dec. 5, 1899Keith and Erickson; 672,942, Apr.` 30, 1901, Keith and Erickson.

We' do not illustrate lall of the apparatus at the ,subscribers station for the lreasons already given. Here also our invention may be practiced with several Atypes of ap- In this systemall talking circuits are metallic, that is are composed of two. line wires; and vin addition we employ a ground return. Each line terminates in the central oilice in a first lselector, corresponding to the answering jacky of a. manual multiple switchboard, andl also# is connected to multiple contacts in theseveral banks of connectors, to which reference will presentlyV bemade.'4 f

Each selector switch is a self-contained unit individual to its line, and each contains a multiple-contact for each of. the second selectors. Each second selector is also a self-contained unit, connected tov its various multiples in the first selectors through l a trunk line, and each contains amultiple contact in its banks foreach' lconnector. Each connector isa complete switch unit connected to its multiples in the various second selector banks .and each connector conv tains in itsI banks contacts for the subscribers lines vfallingowithin its range, usually .one hundred lines.

The mode -of selection of.` a wanted subscriber, briefly' stated', is asfollowsz. lThe calling subscriber, through the .operation of his impulse sender sets the rst selector to connect with an idle second selector in the set containing the thousands terminals-"corresponding to the thousands digit in the number wanted; this cuts off the first selector magnets, whereupon he sets the second selector switch in a similar manner to put himselfl in connection with the terminal contact of an` idle connector in the'hundreds group corresponding to the hundreds digit in the number wanted; thisl cuts off the second selector magnets, whereupon he 'sets the connector switch to select a multiple terminal-vl of the particular line wanted. As the connection progresses step by step, the metallic'talking circuit is correspondingly extended through'the first and second selectorsand the connector, unbroken to the latterbut thereinsepara'ted by condensers. The main battery is bridged across this circuit on the end toward the called subscriber;

but until the latter answers there is no tion with bank contacts fm. and m2.

bridged battery on the calling end. All theY -cut back the main bridged vbattery on the calling end of the talking circuit. When the conversation is finished and the subscribers havehung up their receivers, a release magnet in each of the intermediate circuits trips Athe mechanism and all of the switches are restored to normal.

.Fig. l shows a pair of line wires 1-2 constituting a subscribers line circuit and extending from the first selectorto several subscribers stations A, A', and A2 and A3. The station A is shown in full, connected to the line wires l and 2 by thebranches 3 and 4. The stations A', A2, A3 are all the same as station A, each being connected across the line by its own pair of branches 5-6, 7-8, or 9-10. The line, 1-2 therefore is a party line, and as Will appear later the stations are adapted to be signaled se- "lectively, YAt each subscriber-s station a transmitter T, a receiver R, an induction coil Ic, a switch-hook H, a ringer Q'and condenser C, are provided. In addition to these any suitable impulsel transmitterl is mounted on the set. Each operation of the impulse transmitter sends the Ydesired number of impulses over the vertical side of line, Y

and then a single-impulse over the rotary s1de of line. plain the meaning of these-terms vertical Avandrotary. In connection with the Stroware adapted to pass over and make connec- These bank contacts, as shown in the patents here1 inbefore referred to, are arranged in horizontal rows of ten. The banks of rows are arranged in semicircular form with the center of their radii in the axis of the vertical spindle-o. In order to bring the wipers into contact with any particular .contacts lm. and m2 therefore the spindle o is first stepped up until each wiper is opposite the desired row, and then is turned around step, by step until the wipers come in contact" with the desired particular terminals in-. the row.

The f'rst movement of the spindle is called vthe vertical movement, and the second the rotary movement. From these two descript1ve terms the words vertical and rotary It may be well here to eX- vvertical spindle o (see Fig. .1), carrying vwipers or contact springs fv and o2 which have come to be applied l,to the'two line wires, although in the'presentl system. as will appear later` `the selecting impulsesl are all sent over the vertical'sitle of line.= These terms will be employed herein for convenience to designate the'two line wires. while the various magnets and other parts ot' the apparatus will 'be designa-ted' as vertical and rotary to distinguish their func-A tions. y

Returning tothe subscribers station A we have said -that the transmittenshould send, selective impulses overjthe. vertical side of the line, and a single impulse at ,the .end of each group over the rotary side. his is7 accomplished by a sender`(not shown) acting in Vconjunction with certain'groups of contact springs a, a a, (1.3, a, a5, (a6, a", d?, a", am, a, 1.12, (L13, a, and a, together with the hook lever H. The functions of these'several springs will appear more particularly from the statement of operation hereafter.

The receiver R is shown 'in a locall circuit 21 terminating in one-winding'ot the induction coil l, this being ineifect they ysame as. cutting off the receiver by' a Icondenser so that battery current will not flow. through it and its resistance is removed from the line.. The transmitter circuit for thel comm'on battery system'may be traced as follows: from vertical line wire 11 vby branch 3` wire 25,

spring a., wire 2G, spring a5, spring a, wire 24, springs a and a, line winding ot' induction coil I, transmitter T by wire 23, and thence by wire 22, springs as anda. and wire 21 to the rotary side of line 12, through the branch 4.

The ringer Q is' in a ground tap from branch 4 on the rotary side of line', with an interposed condenser C. The spring af* is grounded at G through a resistance r, for a purpose to be presently disclosed.

It is to be understood that no substantial change is required in the subscribers instrument to convert this system back'into a local battery system, the apparatus remaining the same and the only changes being in the receiver and transmitter wiring.

Passing to the'central oiiice, the metallic talking circuit wires l1 and 12 pass through the first selector b, and terminate in the switch arms f and f2 of what we shall designate as the side-switch F. This sideswitch' comprises four armsinoving together over-a series of contacts, there being threel y contacts for each arm. These arms are lettered respectively f, f, f2, and f3. Arm f cooperates with contacts f", f1", and f2", beingl normally in contact with f". Similarly and synchronously the other arms move over their corresponding contacts during the op eration of the apparatus, being normallyin contact with the point fo in each case.

yThe vertical wire 1l is normally connected through arm f. and Iwire 30 to-the vertical relay D, thence by wire 31 through the cutoff springs '3, k2, and 1 through wire 32 tothe grounded main 'battery B. The ro' tary wire 12 is normally connected through arm. f by wire' 34 to the rotary relay E, thence by wire 33, spring 702 and c, and wire 32 to the same battery.

ln :their normal condition it is apparent that the wires 11-1'2 are severed from the wipers v and in the severed conductors leading from the contacts )C20 to the wiper contacts if. we interpolatethe two equal and opposite windings of a diiierential relay O, shown in the diagram as having an armature o normally.closed,upon a contact 0, con? nected by wire 35 with the busy-switch U,

lthrough the contacts u and u thereofl to the vthis differential relay is used in connection with party lines only. Its winding and con- "nectionsare such'that under normal condiand wire 38 .to the vertical magnet D (which actually does they vertical moving off the spindle o) thence by wire 39 to the main battery wire 32.

The relay E through its armature ycontrols a spring e adapted to close on the same ground contact, spring e being connected by wire 390 to the private magnet P and thence to ythe main battery wire 32. From the wire 390 branch 40 extends to the second contact f1 of the side switch arm f3. lVhen the arm f3 is on this contact the circuit would be continued through 'the back release relay J yto the private wiper v2. Normally however this magnet is cut oil".

The magnet J through its armature j controls the spring contacts y" and j?, which when the armature is attracted ground the wire 41 leading to the release magnet I, which is connected through wire 42 to the main battery' wire 32.- It will be observed that the armature of the private magnet P controls the springs p p2 and p3 the latter two of which also control a ground connection for the magnet l by vway ot' wire 37 and spring lt is necessary however that both magnets D and P be energized in order to close this circuit, and as P is controlled by E, this means that both vertical and rotary relays D and E must be energized.

Although a controlling means is not shown in the drawing the magnet P controls the side-switch F. When the restoring magnet I permits the parts to return to 5 normal, the switch arms of switch F are all returned `to the position shown in Fig. 1. At each retraction of the armature of magnet P these switch arms are all advanced one step by means of an escapement controlled by the said armature. This will be referred to again in the statement of operation.

Before leaving Fig. 1 reference should be -made to the magnets L and N, and also to the arrangement of multiples shown. The magnets L and N are register magnets, and the multiples shown are arranged for party lie signaling. In considering both these let us glance first at the general layout hereinbefore stated. It will be remembered that each line has a first selector such as shown in Fig. 1 This first selector not only has the individual selective wipers v', corresponding to the answering jack, but it 4also has multiple contacts m', etc. (Fig. 2)

.with which these selecting contacts cooperate. These multiples m represent the terminals of wires 13 and 14 leading to thel various second selector switches. These correspond to trunk lines in a `manual eX- change, and as they are only used at any one time by a limited number of subscribers, they are much fewer innumber than the first selectors, say amounting to ten per cent thereof. The same may be said of` the connectors, which are further extended trunks. Now the multiples m in the first selectors represent second selectors, and the multiples in the second selectors represent the connectors. The multiples in the connectors however directly represent and are connected to the subscribers lines andther first selectors. In the drawings Fig. 3 shows a connector. The multiple Vcontacts m5 on the connector for the line 19--20 appear in Fig. 4. The same connector would.

contain a pair of multiple contacts as say m9 (Fig. 1) corresponding to the line 1--2, provided the said line 1--2 fell in the same Ahundreds division, to which that connector is appropriated. Observe the multiple contacts m9-m11-m13 and m15 (Fig. 1) belonging to the line 1-2 are distributed so as to be located in different connectors. The connectors are arranged in groups, and since we use the decimal system in the present case for convenience, each group has the multiple terminals of subscribers whose numbers all have the same hundreds digit. Thus there will be one group of connectors for subscribers from 1 to 100, another group for those from 101 to 200, another 'from those from, 201 to 300, and so on. In the same way the second. selectors are divided 66' into groups according to the'thousands, and

each second selector has multiple terminals for .all theconnectors within its'thousand. Thus there will be multiples in one group of second selectors for all the connectors between 1 and 1000, that is 100, 200, 300, and so on to 900, which within itself selects up to 999. To select a given line the first selector is operated Yto select the thousands or the hundreds group required, and finally the connector is operated to select the line. Byl preference we put the ringing generator connections in the conneet-or circuit, and sincethe connectors are in groups` we can give each of several groups different varlieties of current for ringing, or differently connect the generators, as from one side of the line to ground or from the other side to ground.

Referring now to Fig. 1 which shows a party line havin four telephones, instead of simply multip ying the line to its normal set of terminals as m9 in the first hundred bank connectors (assuming its number we will say to be 12), kit is multipled to the number 12 terminals in the first hundred4 bank of connectors, to the number 12 terminals in the second hundred bank of connectors, to the number 12 terminals in the third hundred bank of connectors, and to be number 12 terminals in the 'fourth hundred bankv of connectors. The bells at stations A, A', A2 and A3 are all in ground taps from the rota-ry side of line, each with a condenser, and each adapted to respond to a different frequency of ringing current, A ifo' 20 cycle current, A to 40 cycles, A2 t`o60 c'ycles and A3 to 80 cycles, for ringing. Four generators are. provided" at the central office, giving respectively 20, 40, 60 and cycle current. Every first hundred group of connectors derives its ringing current from the 20 cycle generator, etvery second hundred group of connectors derives its ringingv current from the 40`cycle generator, every third hundred group from the 60 vcycle generator, and every fourth hundred group from the 80 cycle generator. It will be understood therefore that the multiple contacts m9, m11, m13, and m15 accompaniedl by their private or busy contacts m1", m12, m1* and m1, are distributed in the four groups of connectors referred to, and any station on this line 12 can be selectively rung by' selecting the proper hundreds-group of connectors and then getting vnumber 12. This means that inthe present case subscriberA would be calledas number 12, subscriber A as number 112, subscriber A2 as number 212 and subscriber A3 as number 312. ',The calling 125 subscriber exercises no' judgmentin the matter, but simply'takes'the number as he finds it in t-he directory, and works his transmitter or calling dial accordingly.

It should be noted that by` this arrange- 130 ico ment the number of individual or first selec' tor switches is not increased at all. Neither is thereany increase in mechanism in any of the switches, the only change being that each party line appears in as many groups of connectors as there are subscribers on the line, and each subscriber has his own independent number. Y

Means are thereby provided whereby any subscriber on the line can call any other, and

in fact it is quite possible for a subscriber' `board. XVe state-this analogy because we consider our invention need not be limited describe such a system at length because we do not consider it necessary, for any per son skilled in the art will be able to apply the invention from 'the following description.

There are two classes of calls we wish to register, in-coming and out-going, that is these which originate at other stations but for any reason are reversed, and those originating at the home station, respectively.

Hence we provide two registers, and since out-going calls use the first selector or answering jack swltch, we put the corresponding register in the circuit of that switch, by

means of a branch 421 of the rotary wire 12. It is true that the magnet L is thus included directly in ths talking circuit, butl its impedance may be neutralized by a copper jacket, orI it may be shunted by a non-inductive resistance r', which will pass voice currents without much interference.

In-coming calls come over the multiples,

y hence we put the in-coming or neutral relay N ina branch 4'3 in series with the'connectionsrto the multiple contacts, from the rotary wire 12, the other connectlon `from wire v11 being made by branch 44.

, magnets and apparatus of the latter are cut out, the switch-arms of switch F pass onto their third contacts, f2 (Fig. 1). and the metallic circuit 11-12 is continued through to the conductors 13-14 by way of the contacts c-m.' as indicated in heavy lines.

The operation of the impulse transmitter second' selector.

plete the circuit for releasing the two selecat the substation is repeated to affect the vertical and rotary relays D2 and E2 of the The side switch F" of this selector normally stands with its arms f4, f"' f2, and f7 on their first contacts fo. The 70 wire 13 is connected througha branch 45 with the magnet D2 and thence tothe main battery wire 32. The rotary wire 14 is connected by branch' 46 to the magnet E2 and thence to the'battery wire 32. The armature of magnet D2 controls a spring d and a mechanically connected but electrically insulated spring d2 which 'latter closes on the ground contact g when thearmature is attracted. The armature of magnet E2 con- 80 trols a spring e and a mechanically connected but electrically insulated spring e2 which latter closes on'the ground contact g v when the armature is attracted. The two springs d and e have curved ends adapted to come together when both armatures are' simultaneously attracted at the point marked but not when either armature is attracted Y alone; -When these close together they comtors by magnets J and I through the path: battery B, wire 32, 50, I', 51, 48, e, UZ, 47, 49, m2, c2, 52, J, 53 f3, f20, and ground back to battery. Operated by itself the magnet D2 controls the circuit of the'vertical 95 magnet D3, which' also Apasses through the contacts of the private relay P2,the latterl controlling the escapement of the side switch F', as in the first selector. When the single impulse comes over the rotary side of line 10( as before, this private magnet moves the side switch astep to cut in the rotary mag net E3, and the latter actsautomatically to rotateV the switch, 'as in the first selector, until cutout by the fnalmovementof the side 10E switch to its third contacts and the completion of the talking circuit past the switch.

` Referring to Fig. 3, we will describe the connector apparatus, and then will outline the operation of our entire system. 'ln the 11 firstv place it will be observed that the wires 15 and 16 which constitute the talking circuit through the connector arenot electrically continuous, as they are in the first and second selectors, but are separated in the 11E middle by condensers C, C.

, As a matter of convenience, we have designated the two ends of this connector circuit as 15-16and `15-16. respectively. Connected from the wire 15 by branch 55, is the 12( vertical relay D4, joined on the other side by wire 56 to the spring 57 of a cut-ofil relay R2. This spring is normally in contact with springs 58 and 59, the latter connected to battery wire 32 and the former connected by 12 wire 61 with the spring 62 of the ringing re'- lay W, this spring being normally in contact with spring 63 from which wire 60 leads to the rotary relay E4, and thence to the rotary .side of the li'ne. The relays D4 and E4 13( lclose upon the ground contact.

It will be remembered from the previous statements that theconnector not only steps up its wipers v5 4to the desired row of contacts m5 (Fig. 4.-), but also steps around the wipers to the desired line contact. Hence we have the vertical magnet D5, which does the vertical stepping, controlled by the relay D4, its circuit passing from the spring d4 by way of the wire 64, throught-he normally closed springs p2, p of the private magnet P5, by wire tothe arm f4 of the side switch F2, thence by wire 66 to the magnet D5, and by wire 67 to the main battery wire 32. The first succession of impulses over the vertical wire 15 operates the, magnet D5 through the 1 relay D4. This places the wipers vertically. The singleimpulse over the rotary wire then closes the private magnet circuit, steps the side switch F2 around one contact with all its arms f4, f5", f5", 7. This substitutes for the vertical inagnet D5, the rotary magnet E5. The linal selective impulses over the .vertical wire 15 then operatel the relay -D4 and the magnet E5 'to bring the wipers o5 on the. contacts m5 of theline 19-20 wanted.` This series of impulses is followed by a single impulse as before, over the rotary side `of line, which again actuates the -private magnet and this moves the side switch F2 into its third position so' that its four arms rest upon their lastI contacts f2".. The arms f5 and f5, it will be observed, have com leted the talking circuit (marked in heavy. llnes), and the rotary and vertical magnets are entirely out out; The ringing relay W, however, is cut in by way of wire 69 and Vcontact f2 through wire 65 back to the contacts of relay D4. When the calling subscriber presses his ringingbutton, and thereby grounds the vertical side of line once more, this energizes the relay D4, completing a circuit from ground through springs g2 and'd4, wire 64, springs p2 and p', wire 65, side-switch armf40, side-switch contact f2", wire 69, and relay W to battery. This energizes the ringing relay `W, which breaks the through talking circult and connects the ringing generator wire 170 through v the spring 71 to the rotary wire 16 on the called side of the break, and so to' the wire 18` the ringer Q and ground.

The two magnets R2 and R are bridged across the line, with the main battery interposed. They bothl receive current when the called subscriber answers, this current flowing over the metallic circuit 15-17, 19,- station A4-20-18-16, and back to battery. The cut-on relay R is adapted to complete a bridge across the calling end of the line, in-

cluding the battery B and the relays X and Y, by the following path: battery B, wire 71, relay Y, wire 72spring 73, spring 74, wire 75 wire 16, back to the calling subscribers station through the wires 14 and 12, out again through the wires 11 and 13 to the wire 15, and by wire 76 to spring 77, spring 7 8, wire 79, rela-y X, and ground back to the battery. When the magnet V3 is energized, this bridge circuit is completed andI the talking battery is put on the calling subscribers line. At the same time, however, we cut off the magnets D4 and E4 for the reason thatpif they were left in bridge when the'battery is connected across the line, they would operate simultaneously, and by making contact at the point would close the release circuits of the releasing magnet J2 and of the back release relay J', whereupon the entire connection would be broken down.

To prevent this, we putin the cut-off relay R2. The relays R2 and R." are constructed so as to have the same electrical characteristics. However, relay R is equipped' with a set of springs which make Contact when the relay is energized, whereas the springs of relay R2 serve f to break contact when it is energized. .Consequently if these relays are simultaneously energized the springs controlled by the armatures ofthe relays will affect their operation in such a manner that the springs of relay R2 will break before the springs of relay R make. Conversely, when the relays are simultaneously deenergized, their rel In practice it might be diiiicult to obtain relays of like electrical characteristics; However. notwithstanding this fact, and assuming that the relay Rfmight close its contacts before the relay R2 opens its contacts, the time interval during which the contacts offrelays R and R2 are both closed will be of Such short duration that a relay or electromagnet included in such circuit will not receive sufiicient current for its operation. Obviously if such a condition should arise, it could be readily overcome by making relay R slightly slow to pullyup and to release.

When these relays X and Y are connected. X to the wire 15 and Y to the wire 16, they serve thereafter to control the release circuit, as will be pointed out in the statement of operation.

The relays X and Y, like the relays R2 and R are designed with'like electrical characteristics and control respectively a break and a make contact. These two relays function exactly the same as relays R2 and R', and obviously relay Y could also be made slightly slow to pull up and release. Therefore, when these relays are simultaneously energized, the contact of X will open before the contact of Y closes, and conversely when the relays are deenergized, the contact of Y will open before the contact of X closes. The release circuit controlled by these relays requires the simultaneous closing of the contacts of relays X and Y. If the calling sub-` scriber hangs up his receiver before the called party does, the subscribers loop will be opened at the calling partys station, and this will open the circuit containing the relays X and Y which will therefore be deenergized. However, as the subscriber momentarily grounds both sides of the line directly after the subscribers loop is opened, the relay Y, which is connected from battery to the rotary side of the line, will be momentarily energized and again close its contact. Therefore, as relay X is deenergized and relay Y momentarily energized, the release circuit 70 will be momentarily closed and release the switches. This circuit will be described in detail hereinafter.

We will now refer to Fig. 1a, and will describe the repeating trunk circuit therein shown. rlhe underlying principle of this circuit is that in trunking calls the proper place for the trunk line insertion is before the point of selection of the highest number in any exchange. As will appear from the statement of operation, the rst selectors pick out idle trunk lines leading to the second selectors", simultaneously selecting the thousands number. ln an exchange above ten thousand there would be another set of selectors ahead of the second'selectors, "of course, but the trunk is always inserted after the iirst selector. At this point difficulties are experienced in practice in transmitting the impulses over the trunk line With rapidity and certainty, and this difficulty is heightf ened. by the necessity for the insertion of condensers in the trunks. When then repeaters are used for repeating impulses around thel condensers, the condenser discharge blurs the repeated impulses to a very marked degree. We have found a means to obviate this, and at the same time to provide for certain other requirements in connection with the registering and the control of pay stations. In putting a call through, where it is to be registered at the calling end, as already noted, we have provided a polarized i with the other side of line.

register magnet L (see Fig. 1), which does not respond to the ordinary signaling current to register, but when reversed current is thrown back on the line it does respond to inddicate that a call hasbeen completed. In

order to secure this operation upon the completion of the connection, it will be understood that all that is required is to make the connections .from the main battery to the cut-on side of the connector circuit (see Fig.

3) such that current will flow in the proper, 7,5

will be understood that its use is not limited to this specific system and that it is applicable to any system of signaling in which .repeating is required. f

ln Fig. 1a, which is supposed to be interpolated between. Fig. 1 and Fig. 2, wehave shown the multiple contacts mi in the banks of the first selectors, connected by the trunk wires 13-'14 and 14--13 to a second selector, located at the distant office. Each side of the trunk is conductively divided but inductively made continuous by the condensers C2. rlhe wire 13-14 continues as the vertical side of line, while the wire 14-13 continues the rotary side. lmpulses coming over the vertical side of the second selector cannot pass the condenser C2 directly, but must be repeated. and the same lVe therefore provide the repeater Z, having vitjsfjjrelay .e connected to the Wire 14 by thefwirei90, and by wire 91 through cut-off cont-acts! 92, 93 and 94 to the battery B3. Similarly' the relay a is connected by wire 95 to wire 13 and -thence by wire 96 and through contacts 93 and 94: to the battery B3. The contacts 92, 93 and 94 are normally closed, but adapted to be opened by magnet Z5, which is in a branch circuit 97-98 extending from the battery B3 to two relays Z and Z2 b v branches 99 and 100, and thence to the respective contacts 101 and 102 of the oppositely polarized relays Z? 4and Z4. These relays are in series in the circuit 103, which terminates in the two contacts 104 and 105 lying on opposite sides of the ground contact 108. The armature z2 of the relay 2 controls the long spring 106, and the armature .23 of the relay z controls the long spring 107. and these two armatures also control the springs 104 and 105. When either relay is energized, it grounds its spring 104 or 105, and when both are Y B3 to the back release contacts m2.

energized together they close the contacts 106- and 107 together.

The relays Z and Z2 respectively control the armatures 109 and 110, which in turn control the continuity of the 4branch circuits 111 and 112 with the back supply circuit 113, 114. Each of-these branches has a bat tery connection, and these battery connections are relatively reversed, as shown by the batteries B and B2. Adapted to be bridged across the circuit 113--114 with one or the other of the batteries B or B2, are the two relays Z6 and Z7, the first controlling a front contact 115 and the second a back contact 116. When both relays are'attractf ed, one contact is open, and the armatures are connected in series at 117.- These arma-V tures and these contacts jointly control the continuity of the branch 118 ofthe trunk release circuit 119 leading from the bttery A pall'- allel branch 120 is'controlled by .the two springs 106107.

Impulses over the vertical wire 13 affect the relay a, which repeats into the wire 13 by grounding its contact 105, and thereby grounding the said wirev 13 through the branch 123. Similarly, impulses over the rotary wire 14 affect the relay z, which repeats into the wire 14 by grounding its contact 104 and therebycompleting the vbranch 121. Ordinarily the repetition would be .straight from. wire 13 into wire 14', and

from 14 into 13', but when such is the case the impulses repeated are blurred or somewhat smoothed ou't, 4particularly when transmitted at high speed, by the discharge of the condenser. vWe avoid this by transposing the wires at 125 so that the condenser dis charge in each case is into the opposite wire from that into which the repetition connected through the condensers to the sides in which the respective impulses originate.

The Ioperation of our system, apparatus and methods will have been largely understood from the preceding description; but

we will here briefly review the same.

Taking the system shown in Figs. 1, 2, 3 and 4, we will first assume a call originating over the line 1-2 from the station A (number 12) and intended for station A4 in Fig. 4. Subscriber A first takes down his receiver, R, and turns his impulse transmitter (not shown) so that after the rising of number-of `impulses Sent Vwe Awill' sag vibrating continuously until'cut out.

between the magnet coils and adapted to be i the hook a groundY circuit will be comple-ted from G; through theresistan'ce r and contacts z2- a to the verticahside of line 11, cur-l rent flowing out over this path from the battery through wirel 32, contacts 7c', k2, k3, 70 Wire 31, relay D and line wire 1l. y The first l is one, assumingthe numberof Vstation '4 to be 1920. Relay D controls" magnet- D to step up the Spindle o until thelwipers v register withcontacts\ m in the first row of second' selector contacts in the bank. `As. the impulse transmitter at station A comes to rest, it momentarily 'closes together the` contacts a-a2, which sends one impulse out from 30 battery B through wire 32,` springs cx-c, wire 33 and relay E over wire 34, side switch wiper f2r to wire 12, to` the substation and to ground. Relay E attracts its armature and closes spring e on theground'contact y, thus 85 completing circuit through-the private magnetP, which lets the side switch Fstep around one contact. In doing'vso, the-arm passes onto Contact flo and so cuts in the* magnet E', which immediately takes current 90 through the wire 39, and battery` wirerf 1sA vibration is produced by the armature separating contacts when attracted, this being' represented in the diagram throughout byja ',95- pair of points normally touching each ot er` separated by an insulating point on the armature. The armature also rotates the spindle o so that the wiper 'v2 passes from one 100 pair of multiple contacts to another, touching one before it leaves the last one, and continuingaround until it reaches an idle pair, which means an idle second selector, which again means a selector without any ground on the wire 49. By making the wiper v2 bridge the contacts without a break between ythem it passes over those that are busy because the busy ones being grounded through the wire 49, to hold up the escape magnet P by current over the following path: battery B, 32, P, 390, 40, f1", f3, 53;

J, 52, o2, m2, 49, and ground. The instant an idle selector contact is reached this grounded circuit is broken, and the magnet l5 lets go its armature, with the result that i the side switch F is released to position 3,

the rotary magnet E is vcut ofi' and the arm 7 is open, the arms f and f2 each pass on to its third contact f2", completing the talking 120 circuit and disconnecting the controlling relaysand magnets therefrom, while the arm f3 passes on to its third contact and closes the ground by Wire 54 to the Wire 53 through 4magnet J and wire 52 to the wiper o2, con- 125 insane@ 2). The calling subscriber again turns his transmitter dial to send nine` impulses, by closing the contacts (r- `together nine times and afterwards the contacts [JL-a2 together once as before. The nine impulses cause the vertical relay D2 to be energized nine times over a circuit from battery, Wire 32. through the relay D2, wire l5 and VWire 13, back through Wire 11 to the substation. The relay D2 attracts its armature nine times to ground the spring d2 thereby closing the circuit of the vertical magnet D3 nine times, which steps up the spindle a of the second selector nine rows to ther row of the nine hundreds in the connector contacts m2. The single impulse that follows over the rotary Wires 12 and la passes through the relay E2, which grounds the spring e2 and thereby closes circuit from battery, Wire 32, through the private magnet P2, the latter permitting the side switch F to more all its arms f4, f5, f5 and f7 around one step, the arm f* cutting in the rotary magnet E3, and the arm f5 connecting the Wiper a4 back through the magnet J and P2 to the battery Wire 32. The

rotary magnet, being in circuit, commences to vibrate and step around the spindle i: as before, until the Wipers r3 and wiper 'at nd contacts of connectors that are idle, or, in other words', ungrounded. 1n this connection We should call attention to the fact that the instant the spindle u in Fig. 1 (rst selector) commenced to rise, it released a spring 'u (see the left-hand side of the figure) of a switch U, breaking circuit with contact u of the bridging cut-of relay K, and grounding the Wire 35 on the Contact u2. This completed a circuit from ground as follows: G, u2, u, 35, o', o, 36, and to all the contacts m1", m12, m14, and 'm25 in the multiple banks of connectors upon which connection mightV be made with the line 1 2. These private bank contacts all being grounded, will test busy, therefore, if anyone else attempts to break in by calling line 1-2. Similarly, the

instant connection was made between the first selector and the second selector at v2,

m2, the side switch arm f3 moved into its third position, connecting ground on the Wire 54: and so through the Wire mag- Vnet d, and wire 52 to the Wiper r2,

' through magnet P2 ig. 2) is broken. the

side switch F makes its last step, the arms f5 and f complete Vthe metallic circuit 13 1-lf onto 15-16, the arm f* cuts od the rotary magnet E3, and the arm f5 connects the ground of cont-act f2 to the magnet J. and so to the Wiper e4, which, being on the con- The circuit has noT been traced to the connector shown in Figure 3, with a. clear metallic circuit made up ot wires 11, 13, 15, on one side, and 12, 14, 16 on the other side. rihis is the connector, which actually selects the contact'of the line wanted. le iind the side switch F2 present in this case also, and that it ,controls the circuits of three magnets, the `vertical magnet D5, the rotary magnet E5, and the ringing relay El?.

The subscriber now sends the number 2,. which causes two impulses to pass along the Wires 15, 13 and 11 and to ground at station A, through the connector circuit as follows: battery, Wire 32 to spring 59, to springs 58 and 57, Wire 56, relay D* and Wire to wire 15. This vertical relay D4 is thus energized and it in turn closes a circuit containing magnet D5 which then steps up the spindle e until its Wipers 'v5 and v reach their respective second rows of subscribers contacts. The single impulse over the rotary side 16 of the line from the battery B by 1Wire 32, springs 59-58, wire 61, springs 62-68, Wire 6G, to relay E4, wire 16, and back to the subscribers station operates relay E* which grounds the .spring e4, closing the circuit of the private magnet P2` 1n moving its armature', the magnet P3 lets the side switch go around one contact, cutting in the rotary magnet E5, and connecting the Wiper fu through the arm fo Yand Contact f1", to the spring p3 to prepare ai circuit to release the connector if the de-f sired line is found to be busy.

rlhe subscriber now sends the number O, which is ten impulses over the Vertical side of the line. This again operates the vertical relay D as before, which grounds the spring Z4 and this time closes the circuit c4, p2, p', 65, f4, fw, es, E5, c7, 32. This bringsV the wipers 'v5 and 'v5 onto the individual contacts m5 and m5 in the multiple bank of the connector S2 in Fig. Il. The grounding of the rotary side of the line at the substation will operate relay Et. operation of relay E* will close the circuit containing magnet P3 and the operation of the latter will close a contact at sprlngs p3 and p4. Now, if the called line is busy, the Contact m5 will be connected to ground, as a result either of the operation of switch U (Fig. 4) or, due to the ground circuit, to Wiper v6 by Way of side switch arm. f7 of the switch used in the set-up connection. rlherefore, when the magnet P5 is operated and the .Wiper Av6 is connected to the terminal of the busy line, acircuit will be completed from ground by Way of wiper lv, arm f5", springs p5 and p4, relay J2, and wire 32 to battery. Thiswill operate the relay J2 which, in attracting its armature,

The

releases the stop pawls which retain the spindle lv in its rotated and elevated position, and thus the switch is restored to Vnormal.

5 The Aoperation of the magnet P3 does not affect the side switch F2, and as the connector switch is released as soon as the magnet P3 is `operated when the called line is busy, the side switch F2 is likewise released and'cannot pass out of its normal position when the magnet P3 is deenergized.

The calling subscriber will next operate his ringing button. This will close a circuit containing the vertical relay D4 over a path to ground, from the subscribers station (Fig. 1)', through resistance r, contacts a4, a3, w13, all, a6, and a5 to wire 26, and thence by wires 3, 11, 13 and 15 to the vertical relay D4, wire 56, springs 57, 58 and 59, wire 32 to battery. The operation of the Vertic-al relay D4 will close the circuit of the vertical magnet D5, which in turn will raise the spindle o one step. As soon as the switch takes its first vertical step from normal, springs 101 and 102l of the off-normal switch close and thereby complete a circuit fromv ground to the secondary busyback transformer H, springs 101` and 102 and 'side switch arm feo to the rotary side of the line, and thence out to the substation and back of the vertical side of the line and through relay DA, to battery. This gives the callin subscriber a busy tone. The calling subscrier will then hang up his receiver and will therefore momentarily ground vboth sides of the line which will simultaneously operate relays D4 and E4. These close their contact springs cl2- e3 at point m, whereby the following circuit is completed: batteryB, wire 32, magnet J2, e3, d3, wire v700 to` contacts m", wiper o, relay J arm 7", 'contact/:2 and ground. The relay J and magnet J2 both act, the latter to restore the connector S2 and the former to close the circuit B, 32, 50, magnet I', 51, 49, m2, '02, 52, relay J, 53, armfs,

contact f2", 54, and ground, whereupon the magnet I pulls out the pawls that hold the spindle c ofthe second selector S (Fig' 2,) and restores this to normal. The relay J closes the circuit of the release magnet I as follows: battery B, 32, 42, I,l 41, y2, j, and to round," whereupon magnet I pulls out the )awls from the spindle /v of the first selector,l {(F ig. 1) S, and permits it to go to normal. The magnet I, magnet I and magnet J2 in each case, when releasing the pawls from the switch spindles also pulls over the side switches F, F or 1F2 to the normal or zero position shown in the figures. When the spindle/v of the first selector S drops down, it takes the ground ofi' the wire 35 by Apushing down the spring u of the switch Thus all parts are again normal and all switches idle.

Suppose, however, that the line wanted does not test busy. The subscriber, after sending in his last number presses his ringing button which closes a contact at the springs au13 and a to ground the vertical side of line as follows: G, r, springs t4-w3, 1.13, am, a6, 1.5 and by wire 26 to the vertical side of line. This permits current to pass back from battery, wire 32 in Figure 3, through vertical relay D4 to the subscribers station and ground.- The spring d4 is again grounded, and a circuit is completed from ground, through springs p2-p and wire 65 to arm fw, contact f20, wire 69, the ringing relay W and battery. This relay attracts its armature opening the vertical side of line 15 entirely. It also opens the rotary side of line 16 and connects the forward endand the ringing relay in Figure 3 deenergize' and the metallic talking circuit is clear through from one station to the other, as marked in heavy lines, except for the interposed condensers C. All magnets and re* lays are disconnected, and all grounds are Y cut off, except that the relays VD4 and Ff* are connected from the vertical and rotary side of. the line, respectively, to the springs of othe cut--oif relay R2, and these springs in turn are connected to the battery B; where" as the relays R2 and R are connected in seyries with the battery B, this circuit being bridged acrossthe wires 15`16 leading to the called subscribers station A4. The latter bridged connection is adapted to give current to the subscriber A* in Figure 4 over his metallic circuit; but it should be particularly noted that there is no bridged talking bat tery on the metallic circuit back to the calling` subscriber.

he called subscriber A4 we will suppose now answers by taking down his receiver. Hisswitchhook thereupon rises and closes his metallic talking circuit, whereupon current iows from the bridged battery through the two relays R2-R out to the station A* and back. Both relays attract their armatures, but the springs of relay R2 break con tact before the springs of relay R make contact, and thereby cut off the vertical and rotary relays D4 and E, before the relays X and Y are cut on, with their bridged battery connections. If it were not for this cut-off there would be a short-circuit ythrough the relays'D4-E4, which were bridged, and they would work therelease mechanism by closin their contacts ZS-es at the point w. lVhen the relay R acts, it cuts on the remassen lays X and Y and bridges the main battery across the connector .wires 15-16, so that talking current now flows back through the metallic circuit to the calling station A. Subscriber A thus gets current for his telephone transmit-ter T.

Both relays X and Y now hold up their armatures during the connection, and it is to be observed that this keeps the release circuits of the back release relays open, because the contacts 06"-002 of the relay X are open, although the others y/-yf are closed. The relays D4 and Ef* being cut-out, their release contacts are open' at av.

At lthe lconclusion of the conversation, when subscriber A hangs up, he breaks the /inetallic circuit and momentarily grounds both sides thereof by closing together the springs al, au. (L12. The opening of the subscribers loop deenergizes the relays X and Y, and the subsequent momentary grounding of both sides of the line momentarily energizes rela-y Y, as previously explained.

This closes a circuit from the ground on side switch contact 722 (Fig. 2), by way of side switch arm f7 and relay J to wiper Contact v4 and contact m, and thence 'by way of wire 700, contacts m2 and wire 70, contact y and y to release magnet J2, and by way of wires 750 and 32 to battery. The release magnet J2 will thus be energized, and in drawing up its armature pulls out the retaining pawl of the spindle c of the connector, Fig. 4, restoring this switch to normal. The relay J', Fig. 2, closes the local circuit of the release magnet I of the second selector through wire 49, and the back release relay J of the first selector, which in turn closes the local release circuit of re'- lease magnet I of the first Selector. The operation of the release magnets associated with the various switches will restore all of these switches to normal.

If the subscriber A4 hangs up his receiver ir'st, the relays R2 and R will be deenergized. -The relay R will be momentaf rily reenergized, however, when both sides of the lines are momentarily grounded. 'llhis will close the release circuit through relay J and magnet J2 hereinbefore described, and the various switches Will be restored to normal in a manner similar to that ldescribed when the subscriber A is the first -to hang up his receiver.

We have thus described the operation of our common battery system for a complete call, cutting back the talking battery to the calling subscriber when the called subscriber answers. It remains to describe the opera-` tion of our trunking apparatus.

Referring again to Figure 1a the trunk line we show is adapted to form an extension from a given rst selector in one oiiice to a group of second selectors in a different office, as stated. 1n Figure 2 will be found a line marked line of trunk connection. The ends of the two wires 13 and 14' in Figurela are supposed to be connected directly to. the wires 13-14, where they are cut by this line, the wire 49 in Figure 2 being the same as wire 49 in Figure 1a. Considering the trunk line to be interpolated between the first and secondselectors, therefore, and having the trunkbroken by the condensers C2, the operation is as follows:

The transmission of` impulses and selection of an idle trunk through its contacts m m2, is the same as before, the first selector then connecting the subscribers line through on to an idle interoiiice two-wire trunk; T he second set of impulses coming over the vertical wire 13 cannot pass on into the second selector circuit direct because of the condenser C2. The circuit now is from the battery B3 (Fig. la), through the springs 94, 93, and by wire 96 to relay 2, wire 95 to wire 13, and so back to the subscribers station and ground over the vertical wire. The Y relay .2 when energized grounds the contact 105 b forcing it against the contact 10S, and there y grounds the wire 13 by the following path: 13', 124, 123, 105, 108, to ground. For each impulse, current'will then fiow back from the battery B, F igure2, through the vertical relay D2, through wire 45, arm f3, Contact f", wire 13, wire 13. (Figure 12), and so to ground as stated. The operation of the mechanism in the second selector circuit is the same as already described.

The single impulse that comes over the-f rotary side 14 travels through the circuit 94, 93, 92, 91, relay z, 90, 14, and over the rotary wire back to the calling subscribers station to'ground. The relay a grounds the contact 104 at 108, grounding the wire 14 through wire 121. The subsequent ilnpulses are transmitted to the selectors and connector in the same manner. This brings us to the next step, which is the cutting back of battery of the` proper polarity when the called subscriber answers. It will be remembered that the direction of'current flow which goes back to the calling subscribers station is determined bythe direction in which the battery Bis connected across the circuit 15-16 by the cut-on relay R in Figure 3. Flow of current from this battery cannot go all the way back to the calling subscribers station, however, because of the condensers, not to mention the drop that would result from the resistance of a long trunk if there were no condensers. `We will suppose the connection to have been completed, and the called subscriber to have answered. His answering energizes the relays R', R2. Relay R2 cuts on the battery B across Wires 15'-16 to send current back from the free pole of the battery through the Wire 16 and from the latter through 14', 121, 104, Contact 130, bridge wire 103,

' in series, baclq to contact 131, spring 105,

wire 123, and wire 13 to the wire 15 and back to the grounded side of the battery.

The direction in which the battery B is connected across the circuit in Figure 3 determines which of the relays Z22-Z4 will attract its armature, for these are oppositely polarized. Supposing it to be Z3, this closes the local circuit 101, 99, relay Z, 98, relay Z5, '97, battery'B3, and ground. Relay Z5 opens the circuits of therepeater relays zand zat' the springs 92-93-94. At the same time the relay Z closes the circuit ground, battery B', 111, 109, 113, relay 26, wire 14, 12, back to the calling subscribers s tation, out again, wire 11, 13, relay Z, wire 114, to ground at the upper armature. of relay Z. In other words, battery B" is bridged across the wires 13-14 in the same direction as'the original battery in the connector circuit, Figure 3. Suppose that current over trunk conductors 13', 14 to have been reversed, then the polarized relay Z4 would have attracted its armature and in operating' relay Z2 would have connected-the reversed battery AB2 to send back current. Thus, the direction of the current supplied to the calling subscriber is controlled through the repeater. Due to the reversal of the current'flow in the rotary side of the line caused by the operation of relay Z2 as described, the central oifice service meter L,

polarized to respond to this current flow,l

would operate. 4 If the trunk line is very long, several of these repeater circuits may be used to off-set the excessive trunk `line resistance. The calling line, even if connected over along distance line, therefore, would receive current oftheproper direction.

This brings us to the question of release ing, which is the last 'step to be considered. Therelays z and a on the calling end of the trunk when they both attract their armatures close the contacts 106 and 107 to7 gether, thereby closing the release circuit traced asfollws: battery B3, wire 119, 107, 106, 119 and contact m2 in the-multiple bank mof-the first selector, Figure 1, thence 'in Figure 1 by wire 52 through relay J and to ground. Relay J operates the release magnet I to return the first selector to normal.`

The simultaneous attraction of the armature of relays z and e will likewise simultaneously ground the two sides 13 and 14 of the trunk circuit by means of their springs 104 and 105. This will cause the restoration to normal of all of the rest of the switches used in setting up the connec- 'occur if the subscriber A hung up without completing the connection. After the called subscriber has answered, however, one of the batteries B or B2 is cut back and bridged across the calling end and at the same timethe relay Z5 opens the contact at springs 92-93-94 and cuts oil" the two relays .e and a. The bridge through these relays is opened to prevent their operation by the bridged battery and a consequent prematurev release of the switches, and to `remove them from -the talking circuit. Some means must therefore be provided for breaking the connection and restoring the first selector in case subscriber A hangs up first. Of course, if the called subscriber hangs uprfirst the relays a and z would again be cut 'in and then, when the calling subscriber hung up, they would act as we have stated to clear out.

The relays Z6 and Z7 serve to oontrol'the release of the first selector switch from the calling subscribers end when the called subscriber has his receiver offthe hook. When the calling subscriber hangs up his receiver before the called subscriber does, he opens at the subscribers station the circuit containing the relays Z and Z7, which will therefore be deenergized. However, the subsequent momentary grounding' of both y sides of the line will reenergize relay Z6.V This closesV the release circuit from ground (F ig. 1), wire 54, side switch contact f2", side switch arm f3 and relay J to wiper o2 and contact m2 (Fig. 12), wire 119, contact 115, and armature of relay Z", armature and contact of relay Z7, wires 118 and 119 to bat- 100 tery B3. Thus relay J will be energized. "The vactuation of relay J will cause the operation of release magnet I which'will restore the first selector switch.

While the invention is shown as applied to a call charging arrangement it isto be understood that it is not so limited but may be used for example in semi-automatic working for operating the calling'supervisory relay to control a lamp to indicate the response of the called party at the distant office.

What is claimed is:

1. In a telephone system, incoming lines,

offices wherein said lines terminate, trunks consisting of two conductors only interconnecting said oiices, automatic switching means,'means for building-up connections by means -of said switching' means and trunks, an electro-responsive device associated with each trunk at the originating office, means operated at a certain stage in establishing an inter-oilice connection to supply current to the trunk to cause the operation of said device, and an electro-respon- 12B sive element controlled by said device. 2. In' la telephone system, subscribers lines, oiiices wherein said lines terminate, ftrunks consisting of two conductors only interconnecting said otlices, automatic switches, means for building up connections by means of said switches and trunk lines, an electro-magnetic responsive device connected to each trunk at the originating ofice, means operated upon the completion ot an inter-oiiice connection to supply current to the trunk to cause-the operation of said device, and an electro-responsive device controlled by said device.

3. In a telephone system, subscribers lines, otlices wherein said lines terminate, trunks consisting of two conductors only interconnecting said ohces, automatic switching means for interconnecting said lines, electromagnetic call charging means for said lines, and means automatically operated by the completion of an interoitice connection to supply current to the interohce trunk to cause the operation of said charging means.

4. In a telephone system, the combination with subscribers lines,'ofces wherein said lines terminate, trunks consisting ot' two conductors only interconnecting said oiiices, automatic switching means for interconnecting said lines, electromagnetic call charging mechanism associated with said lines, means to supply current for operating said switching means that will not operate said mechanism and means to subsequently supply current to said two conductor trunk to cause the operation of said mechanism.

5. In a telephone system, the combination with subscribers lines, oiices wherein said lines terminate, trunks consisting of two conductors only interconnecting said oiiices, automatic switching means for interconnecting said lines, electromagnetic call charging mechanism associated with said lines, means to supply current for operating said switching means which flows in a direction that will not operate said mechanism, and means controlled in i'inally completing an interoice connection to change the current tiow in the said two conductor trunk to cause the operation of said mechanism.

6. In a telephone system, the combination with subscribers lines, offices wherein said lines terminate, trunks consisting of two conductors only interconnecting said offices, automatic switching means, electromagnetic call charging mechanism associated with said lines, means to Vsupply to said trunk and switches in the establishment of a connection current flowing in a direction which will not operate said mechanism, and means controlled in finally completing an interofiice connection to reverse the current flow in the trunk line to cause the operation of said mechanism.

7. In a telephone. system, subscribers lines, a meter for each line, offices wherein said lines terminate, trunks consisting of two conductors only interconnect-ing said oiiices, a meter control relay connected to each trunk, automatic switching apparatus for interconnecting said lines, a source of current supply, and means under the control of the called subscriber to an interoiiice connection for supplying current to the said two conductor trunk to operate said meter control relay to cause the same to operate the calling line meter. f

8. In a telephone system, the combination with subscribers lines, oiices wherein said lines terminate, trunks consist-ing of two conductors only interconnecting the same, automatic switching means, a meter individual to each line, a meter control relay connected to each trunk, and means operated by the response of the called subscriber on an interofiice connection to apply current to said interothce trunk to operate said relay, and a circuit thereby closed to operate the calling line register.

9. In a telephone system, the combination with subscribers lines, a meter for each line, oiiices wherein said lines terminate, trunks consisting of two conductors only for interconnecting said olices, automatic switching means to establish a connection between a calling and a called subscribers line, a polarized relay connected to said interoiiice trunk, means controlled in the final completion of a connection to supply current over said trunk to operate said polarized relay and means controlled by said polarized relay for operating said meter.

l0. In a telephone system, the combination with subscribers lines, olices wherein said lines terminate, trunks consisting of two conductoi's only interconnecting said oiiices, automatic switching means for interconnecting said lines, a polarized register serially included in one limb of each subscribers line, a polarized relay connected to each trunk line, means tosupply ,ourrent for the operation of said switching means which Hows in a direction that will not operate` said register, and means for"supplyin`g current to said trunk line upon the completion ot' an inter-office connection which flows in the proper direction to operate said polarized trunk relay, andmeans controlled by the operation otl said trunk relay forsupplying current to the calling line in the proper direction to operate its register.

11. In a telephone system, the combination with subscribers lines, offices wherein said lines terminate, two conductor trunks interconnecting said offices, a` polarized meter serially connected in each subscribers line, a polarized relay for each inter-oiice trunk line, means to supplycurrent for the operation of said switching means which flows in a direction that will not operate said meter, means for applying current to said trunk line when the connection is completed which flows in the proper direction to operate its polarized relay, and means controlled by said relay for reversing the current flow to the calling line for operating its meter.

12. In a telephone system, subscribers lines, each line provided with a meter, means including a two-conductor trunk line for establishing a talking circuit between a calling and a called line, a relay bridged across the trunk for controlling the meter of a connected calling line, and a second relay connected in bridge of the connected called line for controlling said first relay.

13. In a telephone system, subscribers lines each line provided with a meter, means including a two-conductor trunk line for establishing a talking circuit between acalling and a called line, a relay connected to the talking conductors and individual to each trunk line for controlling the meter associated with a connected calling line, and a second relay connected in bridge of the connected called line for controlling said first relay.

141.Y In a telephone system, subscribers lines, offices wherein said lines terminate, two-conductor-trunks interconnecting said ofiices, automatic switches, means for building up a connection by means of said switches and trunk lines, a polarized electromagnetic device connected to said trunk line at the originating office, means operated upon the completion of a connection for applying current to the interoiiice trunk line which flows in the proper direction to op lcrate said device, and an electro-responsive device controlled by said polarized electromagnetic device.

15. Ina telephone system, subscribers lines, ofiices wherein sald lines terminate, two-conductor trunks interconnecting said offices, automatic switches, means for building up a connection by means of said switches and trunk lines, a polarized relay for each trunk 'at the originating oiiice, means operated upon the response of the called party for applying current of the proper direction to the interv-oflice trunk line to operate said polarized relay, and an electro-responsive vdevice controlled by said polarized relay.

16. In a telephone system, subscribers lines each' provided with a call register, means including a trunk line for establishing a talking circuit between a calling line and a called line, a relay for said trunk line for controlling rthe register associated with a connected calling line, and a second relay for the called line for controlling said first relay.

17. In a telephone system, subscribers lines each provided with a meter, means including a trunk line for establishing a talking circuit between a calling line and a called line, a relay individual to said trunk line for controlling the meter associated with a connected calling line, and a second relay in bridge of the connected called line for controlling said first relay.

18. In a machine switching telephone exchangesystem, subscribers lines each provided witli a meter, means including automatic switches and a trunk line for establishing a talking circuit between a calling and a called line, a relay for said trunk line for controlling the meter associated with a connected calling line, and a second relay for the called line for controlling said first relay.

19. In a machine switching telephone system, subscribers lines each provided with a call register controlling magnet, means including automatic switches and a trunk line for establishing a talking circuit between a calling and a called line, a relay for saidl trunk line, means controlledl in finally completing a connection to supply current over said trunk to operate said relay, and a circuit for operating the call register controlling magnet of the calling line closed by the operation. of said relay.

20. In a machine switching telephone eX- change system, subscribers lines each provided with a call register controlling magnet,

means including a dial at the calling substation, automatic switches controlled by said dial and a trunk line for est'ablishinrY a talking circuit between a calling and a called line, a relay for said trunk line, means controlled in finally completing.' a connection to supply current over said trunk line to operate said relay, and a circuit for operating the call register 4controlling magnet of the calling line closed by the operation of Said relay.

21. In a machine switching telephone exchange system, subscribers lines each provided with a meter, means including automatic switches and a trunk line for establishing a talking circuit between a calling Iline and a called line, a polarized relay for said trunk line, means controlled in finally completing a connection to apply current to said trunk to operate said relay, and a circuit for operating the call register controlling magnet of the calling line closed by the operation of said relay.

22. In 'a machine switching telephone exchange system, subscribers lineseach provided with a meter, means including automatic switches and a trunk line for establishing a talking circuit between a calling line and a called line, a polarized relay for said trunk line,l means controlled by the response of the called subscriber for applying current to said trunk to operate said relay,

cluding automatic switches and a trunk line for establishing a talking circuit between a calling and a called line, a pair of polarized relays for said trunk line, means controlled in finally completing connections to certain of said subscribers lines to supply current to said trunk line to operate one of said relays, a circuit for operating the call charging means of the calling line closed by the o eration of said relay, a circuit for supp ying talking current to the calling line closed by the operation of said relay, means controlled in finally completing connections to others of said subscribers lines to supply current to said trunk line to operate the other of said polarized relays, sand a circuit for supplying talking current to the calling line closed by the operation of said latter relay.

In witness whereof, I hereunto subscribe my name this 20th day of December A. D.,

p JACOB IV. LATTIG. In Witness whereof, I hereunto subscribe my name this 22nd day of December A. D.,

CHARLES L. GOODRUM. 

